Effect of Scanning Path on Microstructure and Microhardness of Laser Cladding Ti-6Al-4V Alloy

Ti-6Al-4V laser cladding layers were performed on the Ti substrate respectively based on four different laser scanning ways by laser cladding with coaxial powder feeding. The results showed that the morphology of cladding layers in heat overlapping was much smoother than cold overlapping. The possibility of appearance of concave-convex would be increased in the laser cladding performed with reverse scanning direction. However with same direction scanning the possibility of distortion of the substrate would increase. The microstructure of cladding layers in four scanning ways all exhibit epitaxial growth huge columnar beta grains in which fine acicular alpha and Widmanstaten alpha lath are distributed. The columnar beta grains and fine acicular alpha formed during cold overlapping were denser than during heat overlapping. Also the microhardness of laser cladding zone was improved compared to the substrate no matter in which scanning way while the microhardness in cold overlapping was higher than that in heat overlapping in the same position of cladding zone.